1. Field of the Invention
The present invention relates to the field of medical devices, more specifically to medical devices intended to treat stenoses in the vascular system.
Balloon dilatation (angioplasty) is a common medical procedure mainly directed at revascularization of stenotic vessels by inserting a catheter having a dilatation balloon through the vascular system. The balloon is inflated inside a stenosed region in a blood vessel in order to apply radial pressure to the inner wall of the vessel and widen the stenosed region to enable better blood flow.
In many cases, the balloon dilatation procedure is immediately followed by a stenting procedure where a stent is placed to maintain vessel patency following the angioplasty. Failure of the angioplasty balloon to properly widen the stenotic vessel, however, may result in improper positioning of the stent in the blood vessel. If a drug-eluting stent is used, its effectiveness may be impaired by such improper positioning and the resulting restenosis rate may be higher. This is a result of several factors, including the presence of gaps between the stent and the vessel wall, calcified areas that were not treated properly by the balloon, and others.
Conventional balloon angioplasty suffers from a number of other shortcomings as well. In some cases the balloon dilatation procedure causes damage to the blood vessel due to aggressive balloon inflation that may stretch the diseased vessel beyond its elastic limits. Such over inflation may damage the vessel wall and lead to restenosis of the section that was stretched by the balloon. In other cases, slippage of the balloon during the dilatation procedure may occur. This may result in injury to the vessel wall surrounding the treated lesion. One procedure in which slippage is likely to happen is during treatment of in-stent restenosis, which at present is difficult to treat by angioplasty balloons. Fibrotic lesions are also hard to treat with conventional balloons, and elastic recoil is usually observed after treatment of these lesions. Many long lesions have fibrotic sections that are difficult to treat using angioplasty balloons.
To overcome at least some of these problems, U.S. Pat. No. 5,320,634 describes the addition of cutting blades to the balloon. The blades can cut the lesions as the balloon is inflated. U.S. Pat. No. 5,616,149 describes a similar method of attaching sharp cutting edges to the balloon. U.S. Patent Publication 2003/0032973 describes a stent-like structure having non-axial grips for securing an angioplasty balloon during inflation. U.S. Pat. No. 6,129,706 describes a balloon catheter having bumps on its outer surface. U.S. Pat. No. 6,394,995 describes a method of reducing the balloon profile to allow crossing of tight lesions. U.S. Patent Publication 2003/0153870 describes a balloon angioplasty catheter having flexible elongate elements that create longitudinal channels in a lesion or stenosis.
While the use of angioplasty balloons having cutting blades has proved to be a significant advantage under many circumstances, the present cutting balloon designs and methods for their use continue to suffer from shortcomings. Most commercial cutting balloon designs, including those available from INTERVENTIONAL TECHNOLOGIES, INC., of San Diego, Calif., now owned by BOSTON SCIENTIFIC, of Natick, Mass., have relatively long, axially aligned blades carried on the outer surface of an angioplasty balloon. Typically, the blades are carried on a relatively rigid base directly attached to the outer balloon surface. The addition of such rigid, elongated blade structures makes the balloon itself quite stiff and limits the ability to introduce the balloon through torturous regions of the vasculature, particularly the smaller vessels within the coronary vasculature. Moreover, the cutting balloons can be difficult to deflate and collapse, making removal of the balloons from the vasculature more difficult than with corresponding angioplasty balloons which do not include cutting blades. Additionally, the axially oriented cuts imparted by such conventional cutting balloons do not always provide the improved dilatation and treatment of fibrotic lesions which would be desired.
In addition to the above, drug eluting stents (DES), although very successful, are not suitable for every patient. Patients undergoing DES implantation are kept under a regimen of anti-coagulant therapy for an extended period of time to minimize risk of late thrombosis. Anticoagulants may cause excessive bleeding and are not recommended for people who are suffering from certain other health problems and/or who might need surgery. Some patients are intolerant to anticoagulants.
For all of these reasons, it would be desirable to provide improved methods, catheters, and systems for performing angioplasty and other vascular interventions for treating vascular occlusive diseases, including but not limited to treatment of hardened and calcified plaque. It would be particularly desirable if such methods and systems could be utilized for other body lumens beyond the vasculature. In particular, it would be desirable to provide methods and systems which could utilize both conventional and novel balloon scoring and cutting structures for delivering therapeutic agents to blood vessels and other body lumens. Such methods and systems could thus disrupt vascular and luminal occlusions in a manner provided by conventional scoring and cutting structures while simultaneously delivering therapeutic agents to the blood vessel, and more particularly to the intimal and subintimal regions of the blood vessel which can be accessed by the cutting element in order to enhance distribution of the therapeutic agents. At least some of these objectives will be met by the inventions described herein below.
2. Description of the Background Art
The following U.S. patents and printed publication relate to cutting balloons and balloon structures: U.S. Pat. Nos. 6,450,988; 6,425,882; 6,394,995; 6,355,013; 6,245,040; 6,210,392; 6,190,356; 6,129,706; 6,123,718; 5,891,090; 5,797,935; 5,779,698; 5,735,816; 5,624,433; 5,616,149; 5,545,132; 5,470,314; 5,320,634; 5,221,261; 5,196,024; and Published U.S. Patent Application 2003/0032973. Other U.S. patents of interest include U.S. Pat. Nos. 6,454,775; 5,100,423; 4,998,539; 4,969,458; and 4,921,984. The following patents describe drug delivery catheters having needle based delivery mechanisms: U.S. Pat. No. 4,578,061, describes needle injection catheters having deflectable, axially advanceable needles. U.S. Pat. No. 5,538,504, describes a needle injection catheter having a transversely oriented needle that is laterally advanced by a balloon driver. Also of interest are U.S. Pat. Nos. 6,319,230; 6,283,951; 6,283,947; 6,004,295; 5,419,777; and 5,354,279. Drug coated stents and angioplasty balloons are described in numerous patents and published applications including U.S. Pat. Nos. 6,280,411; 6,656,156; 6,682,545; and Publication Nos. U.S.2004/0193257; U.S.2004/0208985; and U.S.2005/0033417.